Jet Propulsion Laboratory’s Open Source Rover uses six wheels adapted from Traxxas remote control trucks. Traxxas suspension has a hex shaped mounting point for these wheels, but the ServoCity motor hubs used by OSR does not fit. To bolt these wheels onto those hubs, rover builders need to drill two holes aligned with two diagonally opposite holes on the ServoCity hub. Precisely locating these holes may prove challenging, and some rover builders have offered their solution to the problem. This post outlines my approach.
The heart of my approach is a 3D printed jig that is clamped in a drill press vise. It is tall enough to accomodate one of these wheels, with a cylindrical tip that locates the center hole for the wheel. There are two holes on either side of this tip, corresponding to the locations where we want to drill. For setup, the vise and jig are positioned such that one of the holes are aligned with the location of our drill bit.
Once aligned, a wheel is mounted on the jig and we drill our first hole. Once that is done we turn the wheel 180 degrees. We can visually align the newly drilled hole to the printed hole in the jig, or we can use another drill bit as a locating pin. Drop this drill bit through the just-drilled hole into the 3D printed hole in order to locate the wheel.
This setup has room for improvement in terms of precision. The holes aren’t precisely the correct size so the location pin/drill bit has room to move. But it is sufficiently precise for the task at hand so I didn’t put in the time to revise the jig for additional precision.
The 3D printed jig is shared on Thingiverse, and a video demonstration has been posted to YouTube: